Good teeth brushing habits help people to maintain oral hygiene and avoid tooth decay. In order to keep oral hygiene, people brush their teeth every day with a strong force hoping to prevent their teeth from decay. However, according to a report, researchers pointed out that when teeth are brushed too hard, the surface of the teeth and the gums is damaged, increasing the risk of having decay and periodontal disease.
WO international publication No. 01/21035 discloses a toothbrush which can automatically release excessive tooth brushing force. The brush head of said brush is pivoted on the handle, and two opposite ends of the flat elastic plate connect the brush head and the handle, respectively, so that the angle between the brush head and the handle is a fixed value. When the brushing force is over the predetermined force value, the elastic plate is bent and deformed so that the angle between the brush head and the handle is changed significantly. When the force is continuously applied on the toothbrush with the flat elastic plate, the angle between the brush head and the handle is changed more significantly so that the toothbrush cannot maintain the normal function of a toothbrush; therefore, the damage on the teeth and gums caused by excessive brushing force can be avoided.
U.S. Pat. No. 6,327,734 discloses a sensing and signaling system for tooth brushes which reminds the user that the force applied to the teeth has exceeded a critical value. The toothbrush includes a brush-head member and a dome member which is collapsible and recoverable. The brush-head member includes a striking element extended away from a rear surface of the brush-head member and in contact with a surface of the dome member. When stress from the brush-head member is applied on the teeth of the user, the brush-head member is moved toward the toothbrush and transfers the stress to the dome member by the striking member. When an excessive force is applied by the user to the brush-head against the teeth, the dome member is collapsed so that the brush-head is moved toward the toothbrush to remind the user. When the excessive force is removed, the dome member recovers to the original shape and pushes the brush-head member back to the original position.
Taiwan utility patent No. M492666 discloses a stress control brush, wherein the stress control brush uses feedback from the elastic plate to remind the user that the brushing force is over the predetermined force value. In the stress control brush, the elastic plate connects the brush head and the handle. When the brushing force is over the predetermined force value, the elastic plate is in the collapsed bending state, and the angle between the brush head and the handle is changed significantly so that the stress control brush cannot maintain the normal toothbrush function; therefore, the damage on the teeth and gums caused by the excessive brushing force can be avoided. The brush head has a limiting part, and the handle has a limiting part. When the elastic plate is in the collapsed bending state, the limit parts of the brush head and the handle abut against each other so as to restrict the bending curvature of the elastic plate.
Although the tooth brushes described above are capable of notifying users whether or not the stress applied to teeth during brushing hurts the teeth and gums, some problems still exist with these tooth brushes. The tooth brush disclosed in the WO international publication No. 01/21035 has a problem that when the stress exceeds a predetermined value, the angle between the brush head and the handle is changed significantly and is temporarily disabled, and the tooth brush could even generate a plastic deformation which makes the tooth brush disabled; moreover, the predetermined force, which causes the deformation of the tooth brush, and the actual trigger force, which causes the deformation of the toothbrush when users are brushing their teeth, are different each time. If users want to clean the particularly dirty parts of the teeth such as the residue between teeth, this toothbrush may not fulfill the users' demands of having to brush with a stronger force.
The tooth brush disclosed in U.S. Pat. No. 6,327,734 has complicated structures and mechanisms of force transfer, and the structure of said tooth brush is also complicated to assemble. When the toothbrush is in use, the complicated structure and the tiny interspaces cause the deformation trigger force of the brush could be different each time, and the residues and contaminants are easily kept inside the brush head which is hard to be clean up and hard to keep dry. Bacteria significantly grow when the environment is too humid and the residues and contaminants are kept in the brush head such that this brush easily becomes unclean and increases the possibility of inflection.
The stress control brush disclosed in Taiwan utility patent No. M492666 has an elastic plate having a slight bending state and a collapsed bending state when the stress control brush is in use. The difference between the elastic coefficient of the elastic plate in the slight bending state and the elastic coefficient of the elastic plate in the collapsed bending state is small, and some users may not be able to feel the force feedback generated by the elastic plate when using this stress control brush.